From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Trahe, Fiona" Subject: Re: [PATCH] crypto: remove unused digest-appended feature Date: Thu, 17 Nov 2016 17:52:59 +0000 Message-ID: <348A99DA5F5B7549AA880327E580B43589136390@IRSMSX101.ger.corp.intel.com> References: <1479403997-15437-1-git-send-email-fiona.trahe@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "De Lara Guarch, Pablo" , "Griffin, John" , "Jastrzebski, MichalX K" , "Kusztal, ArkadiuszX" , "Trahe, Fiona" To: "dev@dpdk.org" Return-path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id B98825585 for ; Thu, 17 Nov 2016 18:53:02 +0100 (CET) In-Reply-To: <1479403997-15437-1-git-send-email-fiona.trahe@intel.com> Content-Language: en-US List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Note, this is a cover letter - see important clarification below. Sorry, I missed adding the [PATCH 0/1] and [PATCH 1/1] to the email subject= . > -----Original Message----- > From: Trahe, Fiona > Sent: Thursday, November 17, 2016 5:33 PM > To: dev@dpdk.org > Cc: De Lara Guarch, Pablo ; Trahe, Fiona > ; Griffin, John ; Jastrzeb= ski, > MichalX K ; Kusztal, ArkadiuszX > > Subject: [PATCH] crypto: remove unused digest-appended feature >=20 > The cryptodev API had specified that if the digest address field was > left empty on an authentication operation, then the PMD would assume > the digest was appended to the source or destination data. > This case was not handled at all by most PMDs and incorrectly handled > by the QAT PMD. > As no bugs were raised, it is assumed to be not needed, so this patch > removes it, rather than add handling for the case on all PMDs. > The digest can still be appended to the data, but its > address must now be provided in the op. >=20 > I've added this cover letter to pre-empt the question which will arise > in chained-mbuf case. > (Chained-mbuf support will be added in next few weeks for 17.02) > In a chained-mbuf case, if the digest is appended to the data, it could > in theory end up split across the last 2 mbufs. Using the digest address > field only works for the case where the digest is in a flat buffer. The > digest-appended feature would have provided one way of handling this, > pushing the responsibility down to the PMD to follow the chain to find > the digest address and handle it whether in 1 or 2 mbufs. > However, this is adding extra cycles on the data path in all PMDs > to handle a case which may not arise in many applications. > The alternative is to give the application the responsibility > to make sure the digest is in a flat buffer. > Specifically if an application knows cases of a digest spanning > buffers can arise, then it can check for this case and memcpy the partial > start of the digest from the second last buffer into the last buffer > so it's no longer split. > Does anyone see a problem with this? >=20 >=20 > Fiona Trahe (1): > crypto: remove unused digest-appended feature >=20 > drivers/crypto/qat/qat_adf/qat_algs_build_desc.c | 2 ++ > drivers/crypto/qat/qat_crypto.c | 18 +----------------- > lib/librte_cryptodev/rte_crypto_sym.h | 10 +--------- > 3 files changed, 4 insertions(+), 26 deletions(-) >=20 > -- > 2.5.0